The present invention relates to a process for producing nickel electrodes having enhanced active mass utilization for use in primary or secondary batteries. The disclosed process is an electrochemical process which involves the deposition of selenium or tellurium or mixtures thereof onto nickel electrodes. The fundamental reaction, for operation of the nickel-alkaline secondary battery is as follows: ##STR1## The reverse reaction, the conversion of Ni(III) to Ni(II), is the fundamental reaction for operation of the nickel alkaline primary battery.
In conventional secondary batteries, about 50 percent of the nickel goes to an inactive plaque (current collector and support structure). The remaining 50 percent of the electrode is in the active mass. Even when the efficiency of the active mass utilization is 80-90 percent, the total utilization of nickel in the electrode is only approximately 40-45 percent. Thus, nickel, a relatively expensive material, is poorly utilized.
Several techniques have been described to improve the utilization of nickel in a nickel oxide positive electrode. Techniques such as pressed powders, plastic bonding and other improved techniques, including one called "Controlled-Micro-Geometry" employing perforated thin sheets of nickel laminated to a desired thickness and impregnated with the active mass, have been described. These techniques have improved the total utilization of nickel, but have increased the fabrication costs for the electrode.
In addition, techniques of improving nickel active mass utilization have been described involving codeposition of cobalt hydroxide with the nickel or solution doping the nickel with lithium. While cobalt codeposition does substantially improve nickel utilization, the cost of even 5-10 percent of cobalt substantially increases the cost of the electrode. While doping with lithium does produce a beneficial effect, the effect is lost once the nickel oxide becomes saturated with lithium, through formation of LiNiO.sub.2.
The use of nickel plates are electrodes for oxygen evolution has been described in U.S. Pat. No. 4,115,238 to Cipris (1977) and in D. Cipris et al., J. Electroanalytic Chem. Volume 73, p. 125 (1976). In these disclosures, nickel is coated by treatment with selenious acid and/or the equivalent tellurous acid, or both, followed by heating in air. The application of these electrodes, however, was under sufficient voltage to generate oxygen at the electrode, and no cycling was performed of the nickel oxide-selenium coated electrode charged and discharged states.
In a copending commonly assigned application filed herewith Ser. No. 434,983 filed Oct. 18, 1982, Cipris and Walsh disclose a secondary battery comprising a nickel oxide positive electrode, an alkaline electrolyte and a negative electrode wherein the nickel oxide positive electrode is thermally doped with selenium and/or tellurium. Cipris and Walsh additionally disclose a process for forming the nickel oxide positive electrode from a nickel powder by contacting the nickel powder with a selenium and/or tellurium containing aqueous solution, heating the nickel powder in the presence of an oxygen-containing gas, then forming the powder into an electrode.